Linq Expression适用于桌面但服务器上有错误

Question

这是我见过的最奇怪的事情，但希望别人有，因为我一无所知。我有以下代码：

 DataTable dt = (DataTable)dataGridView1.DataSource;
        List<InvoiceItem> itemList = new List<InvoiceItem>();
        int listSize = 30;
        int listIndex = 0;
        try
        {
            itemList = (from DataRow dr in dt.Rows
                        select new InvoiceItem()
                        {
                            CustomerRef = dr["CustomerRef"].ToString(),
                            Description = dr["Description"].ToString(),
                            ItemRef = dr["ItemRef"].ToString(),
                            Rate = Convert.ToDouble(dr["Rate"].ToString()),
                            Quantity = Convert.ToDouble(dr["Quantity"].ToString()),
                            PONumber = dr["PONumber"].ToString(),
                            UnitOfMeasure = dr["UnitOfMeasure"].ToString(),
                            RefNumber = dr["RefNumber"].ToString(),
                            Total = Convert.ToDouble(dr["Total"].ToString()),
                            Address1 = dr["Address1"].ToString(),
                            Address2 = dr["Address2"].ToString(),
                            Address3 = dr["Address3"].ToString(),
                            Address4 = dr["Address4"].ToString(),
                            City = dr["City"].ToString(),
                            State = dr["State"].ToString(),
                            PostalCode = dr["PostalCode"].ToString(),
                            ServiceDate = string.IsNullOrEmpty(dr["ServiceDate"].ToString()) ? (DateTime?)null : DateTime.Parse(dr["ServiceDate"].ToString()),
                            TxnDate = string.IsNullOrEmpty(dr["TxnDate"].ToString()) ? DateTime.Now : DateTime.Parse(dr["TxnDate"].ToString()),
                            Note = dr["Note"].ToString()



                        }).ToList();

            List<string> list = new List<string>();
            list = loadItems();
            List<InvoiceItem> createNewItemsList = new List<InvoiceItem>();
            foreach (var importing in itemList)
            {
                var matchingvalues = list.Where(l => l.Contains(importing.ItemRef));
                //If there is no match in Quickbooks already...
                if (matchingvalues.Count() < 1)
                {
                    createNewItemsList.Add(new InvoiceItem
                    {
                        ItemRef = importing.ItemRef,
                        UnitOfMeasure = importing.UnitOfMeasure
                    });
                }
            }

以下是loadItems（）的代码：

        private List<string> loadItems()
    {
        string request = "ItemQueryRq";
        connectToQB();
        int count = getCount(request);
        IMsgSetResponse responseMsgSet = sessionManager.processRequestFromQB(BuildItemQuery());
        string[] itemList = parseItemQueryRs(responseMsgSet, count);

        disconnectFromQB();
        List<string> list = new List<string>(itemList);
        return list;
    }

以下是错误视图：

这里显示了列表计数：

当我在桌面上运行此代码时，如果 matchingvalues.Count（）= 0 ，它会正确执行代码。但是，当我在服务器上的调试中运行完全相同的代码时，该行代码错误输出＆＃34;对象引用未设置为对象的实例。＆＃34;任何人都可以解释为什么会发生这种情况以及是否有任何解决办法？